If you like to use DailyTech as a source, why not use AnandTech? It does own DailyTech after all.
http://www.anandtech.com/video/showdoc.aspx?i=2988&p=1
@Heaven
The only difference is 320 MB of memory. If you're running at a lower resolution, just stick to a 320 MB version. At higher resolutions however, the extra graphics memory a 640 version has helps it a considerable amount.